Conventionally, as image forming apparatuses such as printers, facsimile machines, copiers, and plotters, or multifunction peripherals having these functions, there have been known liquid jet recording type image forming apparatuses including a liquid jet head.
The liquid jet head (hereinafter, may be referred to as “inkjet head”) includes nozzles from which ink droplets are jetted, a liquid chamber (may be referred to as “pressurizing chamber”, “jet chamber”, “pressure chamber”, and “pressurizing liquid chamber”) leading to the nozzles, and a pressure generating means (may be referred to as “driving means” or “energy generating means”) for pressurizing an ink in the liquid chamber. Upon actuation of the pressure generating means, the ink in the liquid chamber is pressurized, and ink droplets are jetted from the nozzles. The inkjet head is formed by bonding a flow path substrate over which a flow path such as the liquid chamber is formed, and a nozzle plate having the nozzles with each other.
The members to constitute the inkjet head are bonded by, for example, adhesive bonding using a wet glue, a film adhesive, or the like, direct bonding or eutectic bonding via a metal material when silicon substrates are used as the liquid chamber substrate and the nozzle plate, or anodic bonding when metal materials are used as them.
In the inkjet head, end portions of the bonded regions are exposed to the ink, and the pressure for ink jetting is applied to the junctions of the members. Because these members are used at a jetting cycle of several kHz and receive high-frequency pressure fluctuations, their bonded portions degenerate easily. Hence, these members must have a greater liquid resistance than required in bonding of ordinary materials.
In bonding two members, it is generally required to bond them with a high reliability by maintaining part accuracy. However, many of the bonded portions of the inkjet head contact the ink, and the contact with the ink degenerates the adhesive resin layers themselves, or the ink permeates the bonding interface to cause debonding, leading to a significant problem in terms of reliability. Therefore, the resin layers are requested to have a resistance to the ink used, and a sufficient bonding strength with maximum rejection of permeation to the bonding interface leading to debonding. However, there have been no adhesives available that are advantageous with all kinds of inks, and it has been extremely difficult to select an adhesive that is low-degenerative with a specific ink.
Meanwhile, in recent years, home-use inkjet printers and industrial inkjet plotters have become widespread. Hence, there have been increasing opportunities of jetting water-based inks or oil-based inks, and adhesives suitable for these inks have been discovered.
However, the latest efforts of development are directed to inks for suppressing curls of paper media when printed, and inks to be printed on non-absorptive film media, which have different properties from conventional water-based inks and oil-based inks. For example, a curl suppression ink as presented in PTL 1 has a composition in which the water content of the ink is reduced while a solvent is increased, which leads to a strong expression of the characteristics of the water-soluble solvent, instead of the characteristics of the water as in conventional water-based inks. Further, an ink to be printed on non-absorptive film media as presented in PTL 2 is an ink containing a solvent having a high dissolving ability such as methyl pyrrolidone in a high amount, and hence more aggressive against organic substances than conventional water-based inks.
A characteristic difference of these inks from conventional water-based inks is that although they are inks containing water, they strongly express characteristics of an organic solvent and have a greater permeability into an organic structure. Hence, there are problems that adhesives that have been used for water-based inks would be permeated by these inks easily, and that these adhesives would also receive permeation of water at their interface, to thereby lose their bonding strength significantly on a material having hydrophilicity on its bonded surface, such as metal and oxide.
Hence, it is requested to provide a liquid jet head that includes a resin layer having a high organic solvent resistance and curable at a low temperature, and that has excellent initial bondability and bonding reliability.